The invention relates to marine fuel supply systems for fuel injected internal combustion engines, particularly where boating regulations prohibit fuel return from the engine to the remote fuel tank.
In fuel injected engines it is important to accurately control the quantity of fuel delivered to the engine through the fuel injectors. Many systems have been designed to control the operation of a fuel injector to accurately meter the fuel to the engine. It is common to use a high pressure pump to supply fuel to the injectors, with a pressure regulator providing an essentially constant fuel pressure at the injector. When the engine is located a significant distance from the fuel tank, it is common to provide a high capacity pump and recirculate excess fuel, i.e. the amount of fuel over and above that required by the engine, back to the fuel tank. In marine applications, however, it is undesirable to provide an extended fuel return line to the fuel tank, since fire or other hazards could arise.
Some prior systems have used recirculating type fuel injection pumps, with the excess fuel returning immediately to the inlet of the pump. In such systems, however, if the engine is operated at idle or low speeds for significant periods of time, the recirculating fuel accumulates heat from the pump and may vaporize. This typically would reduce the output of the pump to such a degree that adequate fuel pressure could no longer be maintained at the fuel injector.
Copending application Ser. No. 06/808,135, filed Dec. 12, 1985 by Robert J. Hensel and assigned to the same assignee of the present invention, provides a fuel supply system for a fuel injected engine located remotely from the fuel tank, without requiring a pressurized return fuel line between the engine and the tank. Such system includes a vapor separator assuring a vapor free supply of fuel.
The present invention provides another fuel supply system eliminating the fuel return line and eliminating recirculation through the fuel pump. In the present invention, a high pressure fuel line from the fuel injector pump is dead-headed at the fuel injector, i.e. closed-end connected to the fuel injector without a return fuel line to the fuel pump and without a return fuel line to the remote fuel tank. In the preferred embodiment, a differential pressure transducer is connected to sense the differential pressure across the fuel injector and turn off the fuel pump when the differential pressure is above a given value, and to turn on the fuel pump when the differential pressure drops below a second lower value, to maintain a predetermined pressure across the injector and hence an adequate supply of fuel available thereto. The invention also avoids the problem of recirculating oil back in with gas.